Automobiles are routinely supplied with exterior lighting including headlamps, brake lights, and warning lights. Each lighting component has a rated voltage for which the component operates at a given intensity and efficiency. Operation at the prescribed voltage optimizes the lighting component's performance and life expectancy.
Determinants that affect the voltage that is supplied to a lighting component include the ambient temperature and the system voltage signal. At colder ambient temperatures, wire resistance is decreased. As a result, conductivity is increased and more current is able to pass through the lighting component. Also, system voltage increases result in an increased voltage supply to the lighting component. For either situation, the power output across the lighting component will reduce the component's life expectancy due to filament burn out resulting from excess heat generation.
One existing design modification that is directed toward reduced voltage that is supplied to a lighting component includes adding wiring to the lighting circuit in the same manner by which the intensity of daytime running lights is controlled. Daytime running lights are low intensity lamps that improve an approaching automobile's external visibility. Since daytime running lights only need to be relatively dim, the voltage is reduced by increasing the amount of wire in the daytime running lights circuit relative to that of the nighttime headlamps. The additional wire increases resistance in the daytime running lights circuit and consequently reduces the voltage and current passing therethrough. Similarly, voltage and current can be limited to other exterior lighting by simply increasing the amount of wire in the circuitry, thereby ensuring that the rated voltage for each lighting component is not exceeded to a significant extent. One drawback to this solution is the cost and inefficiency associated with supplying and installing the additional wire. Another disadvantage is that added resistance reduces light output, causing the exterior lighting to be too dim while degrading the overall lighting performance when temperatures and system voltage would ordinarily be satisfactory for normal lighting operation. Further, adding a constant resistance only produces a mean shift in voltage, and therefore in lighting performance, and fails to affect voltage variation.
Another inherent deficiency in adding additional wire to a lighting circuit is that the solution does not address problems arising when ambient temperatures are relatively high or when system voltage is relatively low. Increases in ambient temperature increase wire resistance and reduce conductivity, which in turn causes less current to pass through the lighting component. Also, a reduction in system voltage reduces the voltage that is supplied to the lighting component. Either situation causes an undesirable reduction in light intensity from a lighting component.
Accordingly, there is a need for a system that consistently provides voltage to lighting components at a predetermined level such as the component's rated voltage. There is also a need to provide such a system that reduces voltage variation without reducing the light intensity from the component, and that can be implemented at a relatively low cost.